Electron tube



2,869,009 Fatfented Jan. 13, 1959 ELECTRON TUBE Merrald B. Sllrader, Mount Joy, Pa., assignor to Radio Y 6 Claims. (Cl. 313-39) This invention relates to electron tubes having control electrodes and particularly to such tubes adapted to produce large amounts of power at high frequencies.

In the operation of electron tubes constructed according to conventional designs at the higher power levels, it has been found that control electrodes of the tubes tend to become heated. The heating is produced in part by radiation from the thermionic vcathodes and in part by the interception of electrons by the control electrodes. Such heating causes thermionic emission of elect'rons from the control electrode structure and in extreme cases may be suicient to cause the destruction of the control elements of the electrode structure by melting or distortion.

It is an object of this invention to provide an improved control electrode structure for an electron tube which is adapted to be eciently cooled.

It is a further object Vof this invention to provide an electron tube of improved design.

` Brieily, an electron tube according to this invention comprises a hollow anode, and a control electrode comprising a tubular supporting member extending at one end onto the anode and closed at that end by a hermetic seal, a plurality of spaced vanes mounted on the outer surface of the tubular member extending longitudinally thereof and outwardly therefrom forming a plurality of longitudinal channels along the tubularmember, and a plurality of turns of wire mounted on the outwardly extending ends of the vanes, each turn extending across all of the longitudinal channels. According to one feature of this invention, an elongated shield member of U-shape, or 'channel-shape, cross-section extends within and along each of such channels in spaced, insulated relation thereto. According to another feature of this invention, the tubular supporting member may be mounted on a metallic header member with the tubular member extending normally from the header member and the open end of the tubular member hermetically sealed to the header member. An opening through the header member and communicating with the tubular member is provided to enable the introduction of cooling fluids into the tubular member. One or more elongated cathode filaments extends within and along each of the channels. The lead-in means for the cathode la- 2 L Figure 2 is a view in cross section taken along lines 2-2 of Figure 1 and;

Figure 3 is a view, partially in cross-section, taken along lines 3 3 in Figure 1, and showing the mountingrmeans for the channel shape shields.

Referring to Figures 1 and 2an electrode structure' according to one embodiment of this invention comprises a metallic header member 10 in the form of a dish or anged cup. A tubular supporting member 12 is brazed or otherwise hermetically mounted, at one end, on a central portion of the header member 10 and extends normally from such header member. The other end of the tubular member 12 is closed by a hermetic seal as by a plate or disc 14 brazed or otherwise sealed across the end of the tubular member 12. An opening 16 in the header member 10 communicates with the interior of the tubular member 12 to provide for the introduction of cooling fluids, such as air or water, into the tubular member 12.

A plurality of ribs or vanes 18 are mounted on the tubular member 12 and extend longitudinally along and radially outward from the tubular member, forming a plurality of longitudinal channels 20 spaced about the outer surface of the tubular member. A plurality of turns 22 of wire are wound about and mounted on the outwardly extending ends of the vanes 18 with each turn extending across all of the channels 20. The tubular mem-ber 12, vanes 18, and turns of wire 22 constitute a control electrode for varying the electron current of the tube.

The tubular member 12 and the vanes 18 are composed of a material having mechanical strength and high heat conductivity, such as most metals. The vanes 18 may be mounted on the tubular member 12 by brazing or welding or by force fitting them in slots in the tubular member 12. The wire is composed of a material having high electrical conductivity such as molybdenum or similar metal and the turns 22 of wire may be mounted on the VanesVby brazing or welding or by peening or swag`- ing them into transverse slots (not shown) in the ends of the vanes 18. It will be seen that heat from the turns 22 of wire will be conducted along paths of high heat conductivity from the wire, through the vanes 18, to the tubular member 12 where it may be dissipated into a cooling iluid circulated within the tubular member 12.

In an electron tube, according to this embodiment of the invention, two relatively heavy lead-in conductors 24 are insulatingly sealed through spaced holes 26 in the header member 10. Referring to Figure 1, each leadin conductor 24 is sealed through one of the4 holes 26 by means of a collar or cylinder 28 of insulating material (e. g. ceramic) to each end of which metallic collars 30,

coaxial with such cylinders 28, are sealed gas-tight. The collars 30 may be sealed to the cylinder 28 by any of the methods known in the art such as, for example, by butt welding. rl`he coaxial collars 30 and cylinder 28 are then telescoped over one of the conductors 24, and the collar ments extend through the header member and are ini sulatingly and hermetically sealed to the header member.

A tubular shield or skirt may be conductively connected at one end to the plurality of vanes and at the other end to the header member thus surrounding the cathode filament lead-in means to provide shielding between the cathode and anode. Sorption type gettering means may be provided on the electrode structure.

The invention will be more completely understood when the following detailed description is read in conjunction with the appended single sheet of drawings wherein: Figure 1 is a view in cross section of an electron tube according to one embodiment of this invention;

30 at the upper end of the cylinder 28 is sealed to the edges of one of the holes 26 in the header 16. The collar 30 at the lower end of the cylinder 28 is sealed to the conductor 24. The seals between the upper collar and the header and between the lower collar and the conductor may be made by any means which will provide both mechanical strength and gas tight properties, such as by welding or brazing.

Filament mounting plates 32, and 33 are each eccentrically mounted on the upper end of one of the leadin conductors 24, one of the lea-dein conductors 24 'being shorter than the other so that the plates 32 and 33 may be aligned inoverlapping relation to each other. Each of the plates 32 and 33 has a centrally located opening therethrough of larger diameter than the tubular member 12 and through which the tubular member 12 ex- 3 tends. The plates 32 and 33 may be welded -or brazed or otherwise attached to the ends of the conductors 24 so as to be mechanically supported by the conductors 24 and at the same time electrically connected thereto. A pluralityof mounting apertures 34 and 3.4 are `provided in circular arr-ay in the upper one of the plates. 32, alternating in size between a rgiven size 34 and an enlarged' size 34. The lower lone of the. plates 33 is provided with` a circular array of apertures 34 corresponding in size to the given. size mentioned above and each aligned with an enlarged aperture34 in the upper plate 32. A plurality `of filament connecting rodsA 36 are mounted in cylindrical array in the apertures above described. The rods 36 correspond in sizeto the apertures 34 of given size, a rod 36 being mounted in each off the apertures 34 of given size in theV upper plate 32 and a rod extending through eachV of the enlarged apertures 3 4 in the upper plate 32 and into an aperture 3,4 in the lower plate 33. The rods 36 may be soldered, brazed orwelded into the apertures 34 to provide mechanical support and electrical connecttion for the rods 36.

A plurality of self-supporting hair-pin type cathode filaments 38 are mounted on the connector rods 36, one end of each lilament lbeing connected to one rod and the other end being connected to an adjacent rod. As shown in Figure 2, one hair-pin filament 38 is contained within each of the channels 2t) formed by vanes 18 on the tubular member 12. A top cap 40 spaced from `the .closed end ot the tubular member 12 and having iiexible hooks or ngers engaging the `bites or folds in the filaments 38 is provided for binding the upper (or bite) ends of the lilaments together and imparting` mechanical rigidity to the filament structure.

According to this embodiment of the invention, the cathode filaments 38 may be composed of thoriated tungsten or some other thermionically emissive material land are designed so as to be self-supporting even when hot. However, cathode filaments 38 which are less rigid may be used if a proper tensioning means is provided. Y

The cathode filaments 38 are directly heated by elec- Vtrical current iiowing through them. Electric terminal means 42 are provided on the lower ends of the lead-in conductors 24 to enable the connection of the conductors 24 to a source of electrical energy. The electrical current will ow upwardly through one of the conductors 24, through a iilament mounting plate (e. g. 32) and the filament connecting rods 36 attached thereto, up the leg of each hair-pin filament 38 connected to one of the rods 36 and then down the other leg of the iilaments 38 to a connecting rod 36 attached to the other plate (e. g. 33) and out the other lead-in conductorZiand terminal 42 to the energy source.

A .hollow cup-shaped anode 44 surrounds the electrode structure described `above and is insulatingly and her- Vmetically sealed to the periphery of the header member 19. The anode 4f may comprise .a metallic (e. g. copper) cylinder 46 closed at one end. by a plate 48 hermetically sealed thereto. The other end of the cylinder 46 is hermetically sealed, in end to end relationship, to an insu lating cylinder 50 (e. g. a ceramic cylinder). The hermetic seal between the `anode cylinder 46 and the insulating cylinder d may be a butt weld or braze, for example. The wall ot the anode cylinder 46 may be thinned down adjacent such seal, as shown, to provide a heat dam which will prevent the conduction of excessive heat from the anode 44 to the seal region during operation of the tube, since such heat may destroy the seal, and to permit differential radial expansion and contraction of the anode 46 and insulating cylinder 5d. lTo further protect the seal a shielding ring 52 is mounted on the inner surface of the anode cylinder 46 adjacent the seal region. The shielding ring 52 will intercept electrons emitted by the cathode which otherwise would bombard and heat the seal region and cause possible destruction of the seal.

The lower end oi the insulating cylinder 50 is hermetif cally sealed to header member 1t) through a thin metallic collar 54 having `a radially extending ilange 56. The insulating cylinder 5i) is sealed to the collar 54 in end to end relationship by a butt weld or braze. The flange 56 on the collar 54 is then hermetically sealed to a flange 58 on the header member l@ as by welding or brazing to complete the gas-tight envelope of the tube. The thin collar 54 permits differential radial expansion and contraction of the header member 10 and the insulating cylinder 50.

The frange 58 on the header member 10 serves also as the terminal for the control electrode being electrically connected to the turns 22 of Wire through the tubular member 12 and vanes 18. However, to provide a shorter path for high frequency currents from the terminal flange 53 to the turns 22 of wire and to provide shielding between the anode 44 and cathode structure 24, 32, 33, and 36 a tubular metallic shield or skirt 60 surrounding such cathode structure is connected between the header member 10 and the lower extremities of the vanes 18 or the wire`22 thereon. For example, the shield 60 may be welded or brazed'to the header it() and to the vanes .1S 'or wirey 22. To provide further shielding between the anode 44k and the cathode structure including the lilaments 358 `a metallic cap 62 may be welded or brazed to the upper extremities of the vanes 138.

rI he gas-tight envelope of the tube may be evacuated through an exhaust tubulation 6,4 sealed through an opening in the closed end of the anode 44. For example, a metallic tubulation 64 may be welded or brazed into a hole in the plate 4S closing the end of the anode cylinder 4,6. After the tube has been evacuated, the metallic tubulation 6.4 may -be hermetically sealed by a cold pinch'ofl In order to avoid excessive electron absorption by the tubular member 12 and the vanes l1 8 extending therefrom, 4a shield means is provided between the cathode filaments and such tubular member and vanes. The

shield means may comprise an elongated shield 66 of' U-shaped or channel-shaped cross section extending within and along each of the channels 20 formed lon the tubular member 12 by the vanes 18. The shields 66 are adapted to fit inside such channels 20 in spaced relation to the sizes thereof, the orientation of the shields `66 corresponding to that of the channels 2G. rThe shields are electrically connected to the cathode to maintain them at cathode potential. Thus, electrons emitted by the cathode filaments 3S are repelled by the shields 66 producing a beam former action and reducing the number of elecf trous.v intercepted by the tubular member 12 Iand vanes 18 to a negligible value.

Referring to Figure 3, the channel-shaped shields 66 are insulatingly mounted at their lower end on the vanes 13. A tab 68 is provided at the lower end of each side of `the shield' 66. Such tabs 63 extend transversely outward from the shield 66 and under and adjacent vane 13. The tabs 68 are provided with slots 70Y which co-operate with an insulating sleeve '72, and insulating washer 74, and a Ascrew 76 to provide an insulating mounting for the shields 66 on the vanes 1 8.

Referring to Figure l, the upper ends of the shields 66 are provided with tabs 78 which extend transversely inward from the shiel-ds 66 and are all attached to a metallic ring 8.50 which is in turn attached to the cathode top cap 40. The ring 8i) may be attached to both the tabs 78 on the shields 6.6 and the top cap 40 by Welding or brazing to provide both mechanical rigidity and electrical connection.V

The shields 6.6 Amay be 'composedV of any suitable metal such as molybdenum, kfor example. Furthermore, in Order to avoid the deleterious eitects of residual gases which Amay remain in the evacuated envelope due to occlusion in the electrode structure, etc., the shields 66 may .be coated or sprayed. with a sorption type getter material such as zirconium, for example. lt will be seen that the shields 66 are in an advantageous position for heating by radiation from the cathode filaments 38 during operation of the tube. Such heating of the shields 66 is desirable since it has been found that sorption type getter materials tend to occlude different gases more efficiently at different temperatures. lt will be seen that different portions of the shields o6 will tend to be heated to different temperature due to their varying proximity to the intensely cooled tubular member 12 and to the cathode filaments 33. The getter material on the shields 66 will thus efficiently occlude the different residual gases which may remain within the envelope after evacuation or which may be evolved during operation.

It will be seen from the above that an electron tube according to this invention is free of the problems, tofore encountered in similar electron tubes of conventional design, relating to overheating of the control grid structure. For this reason, the control grid structure may be adapted to provide sensitive control over the operation of the electron tube placing the grid elements or wires 2.2 in close proximity to the cathode filaments 38 since there is no danger of the grid elements buckling or shifting due to overheating. in addition, according to this invention, the construction of the tube is adapted to the generation and control of large amounts of power at high frequencies. For example, the radial flange on the header member, which serves as the control grid terminal, is peculiarly suited to the introduction of high frequency excitation into the tube and the extraction of high frequency power from the tube.

Those skilled in the art will find many new and useful applications for the electron tubeherein described, particularly in View of the fact that the structural and design features thereof make possible the simple and inexpensive fabrication of tubes according to this invention.

What is claimed is:

l. An electron tube comprising an anode, a control electrode comprising a support member mounted adjacent to said anode and at least two vanes extending longitudinally along the outer surface of said member and projecting outward therefrom and forming at least one longitudinal channel along said member open toward said anode, at least one elongated filament extending within and along said channel in spaced relation to the sides of said channel, and an elongated channel-shape shield extending Within and along said channel in spaced relation to and between the sides thereof and said filament, said shield having an orientation corresponding to the orientation of said channel and being electrically connected to said filament.

2. An electron tube as claimed in claim 1 and wherein said shield is coated with a sorption type getter material.

3. An electron tube as claimed in claim 1 and where in a plurality of grid wires are mounted on the outwardly extending ends of said vanes and extend across said channel.

4. An electron tube comprising a hollow anode; a control electrode structure within said anode, said control electrode structure comprising a tubular member of heat conducting material projecting coaxially within said anode and having an inwardly extending end and sides in spaced relation to the inner surface of said anode, said end of said tubular member being closed by a hermetic seal, and a plurality of vanes extending longitudinally along said sides of said tubular member and outwardly therefrom forming a plurality c-f longitudinal channels along said tubular member, said vanes being composed of heat conducting material and being mounted on said tubular member in heat conducting relation thereto; a plurality of elongated cathode filaments extending within and along each of said channels in spaced relation to the sides thereof; an elongated channel-shape shield extending within and along each of said channels in spaced relation to the sides thereof and to said filaments, each of said shields corresponding in orientation to the orientation of said channels and being electrically connected to said cathode filaments; and means including said anode and said tubular member forming a gas-tight envelope containing said vanes and said filaments and. said shields.

5. An electron tube comprising an anode, a control Y electrode comprising a support member mounted adjacent to said anode and a plurality of vanes extending longitudinally along the outer surface of said member and projecting outward therefrom and forming a plurality of longitudinal channels along said member open toward said anode, at least one elongated filament extending within and along each of said channels in spaced relation to the sides thereof, and an elongated channel-shaped shield extending within and along each of said channels in spaced relation to and between the sides thereof and the filament therein, each of said shields having an orientation corresponding to the orientation of its channel and vbeing electrically connected to the filament therein.

6. An electron tube according to claim 5 wherein a plurality of turns of grid Wires are mounted on the outwardly extending ends of said vanes, each of said turns extending across all of said channels, Y

References Cited in the file of this patent UNITED STATES PATENTS 1,973,094 Mouromtseff et al Sept. 11, 1934 2,489,872 Elder et al Nov. 29, 1949 2,492,313 Okress Dec. 27, 1949 2,693,546 Sorg et al. Nov. 2, 1954 2,727,178 Dailey et al Dec. 13, 1955 

